1. Field of the Invention
The present invention relates to a light source system for converting a linear light source to a surface light source.
2. Description of the Prior Art
It has been well known to use a linear discharge tube as a lighting source of a microscope because the discharge tube, such as a mercury lamp, has a large amount of light which is desired for the lighting source of the microscope. Such discharge tube can also provides light having a desired wave length. As shown in FIG. 1, the known light source comprises a collector lens 2 having a large aperture in front of a discharge tube 1. Such light source must obtain a predetermined amount of light from the light emitted from a small area shown with reference numeral 1a as a part of the discharge tube 1, so that a large amount of light is lost and heat generation is increased, and as a result, an expensive quartz tube should be used as a discharge tube. In the case of carrying out automatic dimming with the use of a strobo discharge tube, if a distance between electrodes is short, a circuit becomes complicated since an internal impedance of the tube is low and the present technique cannot adjust light.
In addition to this kind of light source systems, there is a system in which a cylindrical lens is used as a lens arranged in front of a discharge tube, thereby reducing magnification in the longitudinal direction, converting a light source similar to a square, and utilizating light from the light source efficiently. Such system, however, is not preferable because illumination blurs are caused if a frosted filter having strong diffusibility is not placed at the image plane.
A light source system is also contemplated wherein the periphery of a discharge tube is covered with one end surface of a bundle of optical fibers, the other end thereof is matched with the necessary surface, and light from the light source is efficiently taken out. In such illuminating system, however, heat radiation is much worse, so that when a large capacity of a strobo is used for a short time interval, forced water cooling is required having a complicated structure. If the inner diameter of an optical fiber bundle is made large for a heat radiation counterplan, the number of optical fibers is increased in proportion to the diameter.